It has been fairly well established that population density in the United States, as measured, for example, by persons per acre has little direct effect on pathological behavior. However, a household survey conducted in Chicago under this grant has shown that crowding in the home, as measured by person per room, has marked pathological effects on the mental health and social relationships of persons living in the home and a marked effect on some aspects of physical health, sexual behavior, and child care. Furthermore, it has been shown that these effects occur not only in highly crowded households but occur within the range of crowding that typically occurs in the United States. It has also been shown that living alone, a phenomenon increasing rapidly in the United States, is related to suicide (using ecological data) and to heavy drinking and mortality due to alcoholism (using ecological and individual data). As the experience and effects of living alone have received very little attention one of the first and more important things that we are doing is to examine the characteristics and experience of these who live alone in some detail. From various sources it is obvious that the effects of the micro or home environment are greatly affected by the characteristics of the individual (age, sex, marital status, health, past experiences with crowding) the household composition (nuclear family, extended family, broken family, etc.) and the organization and function of the household; but what these relationships are is not known. The specification of the interaction of these relationships will be one of the main tasks being studied. Although the macro environment (including density) does not appear to have much of a direct effect there are substantial reasons for believing that it does have strong interaction effects with the various components of the micro environment. The determinations of these interactions and how they relate to living alone and crowding will be the other major component of this study. Three major data sets that combine individual and ecological data are being used.